Zoom in on the South Shetland Islands, just off the northern tip of the Antarctic Peninsula, and you’ll see what appears to be a giant Cheerio floating in the South Atlantic. This is actually Deception Island, an oddly shaped chunk of land that almost completely encircles a 7km-wide natural harbour called Port Foster. It owes its existence to a vast volcanic eruption about 10,000 years ago, which left a crater that was subsequently flooded by the ocean. It’s still rumbling away even today – Mount Pond, on the eastern side of the island, has erupted several times this…